1. Technical Field of the Invention
The present invention relates generally to a bus bar assembly equipped with a first and a second bus bar which are made of a flat strip and to which main electrode terminals of a plurality of semiconductor modules installed in an electric power converter are joined.
2. Background Art
Electric power converters such as inverters installed in electric vehicles or hybrid vehicles are usually equipped with a first and a second bus bar which are made of a flat strip and to which main electrode terminals of a plurality of semiconductor modules are coupled. For instance, the first bus bar is connected to a positive (+) electrode of a dc power supply. The second bus bar is connected to a negative (−) electrode of the dc power supply.
FIG. 8 illustrates a bus bar assembly 9, as taught in Japanese Patent First Publication No. 2007-215340. The bus bar assembly 9 includes a resin-molded body or case 93 in which the first bus bar 91 and the second bus bar 92 are disposed in parallel to each other. The molding of the first and second bus bars 91 and 92 with resin requires keeping the positional relation between them precisely. This is because electrical characteristics such as inductance of or resistance of insulation between the first and second bus bars 91 and 92 depend upon the positional relation between the first and second bus bars 91 and 92, thus requiring keeping the first and second bus bars 91 and 92 in a preselected positional relation within the case 93 at all times. When the first and second bus bars 91 and 92 are insert-molded with resin, the flow of the resin in a mold may result in misalignment between the first and second bus bars 91 and 92, thus requiring the need for holding the first and second bus bars 91 and 92 firmly in the mold. It is, however, difficult to keep the first and second bus bars 91 and 92 simultaneously in place in the mold, thus requiring a complicated structure of the mold to do so.
The covering of the first and second bus bars 91 and 92 with the resinous case 93 will result in a lack of dissipation of heat from the first and second bus bars 91 and 92, which leads to an undesirable rise in temperature of the bus bar assembly 9.
The complete covering of the first and second bus bars 91 and 92 will result in an increase in amount of resin material, which leads to an increase in entire production cost of the bus bar assembly 9.
The first and second bus bars 91 and 92 are, as illustrated in FIG. 9, disposed in the resinous case 93 with connecting terminals 911 and 921 thereof exposed outside the resinous case 93. This requires pieces of the mold to be drawn in four different directions K1, K2, K3, and K4 after resin material is solidified in the mold, thus resulting in a complicated structure of the mold.